I've followed MSDN on how to handle enumerations in Code First for EF6. It worked, as supposed to but the field in the created table that refers to the enumerator is a simple int.
I'd prefer a second table to be produced, the values of which would follow the definition of the enumerator in C# code. So, instead of only getting a table corresponding to Department in the example on MSDN, I'd also like to see a second table populated by the items from Faculty.
public enum Faculty { Eng, Math, Eco }
public partial class Department
{
[Key] public Guid ID { get; set; }
[Required] public Faculty Name { get; set; }
}
Researching the issue, I stumbled upon a solution, which suggests creating a table for the enumeration and populating it explicitly by seeding.
It appear to me as a cumbersome approach and a lot of work that should be handled automagically. After all, the system knows what actual values that constitute the enumeration. From DB point of view it's still data rows, just as the entities that I create but from OO aspect, it's not really a data - rather a type (loosely expressed) that can assume a finite and onbeforehand known number of states.
Is the approach of populating the table "manually" recommended?
Since EF doesn't handle it automatically, yes, this is the recommend way.
I suggest some modifications in article that you provided.
public enum FacultyEnum { Eng, Math, Eco }
public class Faculty
{
private Faculty(FacultyEnum @enum)
{
Id = (int)@enum;
Name = @enum.ToString();
Description = @enum.GetEnumDescription();
}
protected Faculty() { } //For EF
[Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Id { get; set; }
[Required, MaxLength(100)]
public string Name { get; set; }
[MaxLength(100)]
public string Description { get; set; }
public static implicit operator Faculty(FacultyEnum @enum) => new Faculty(@enum);
public static implicit operator FacultyEnum(Faculty faculty) => (FacultyEnum)faculty.Id;
}
public class ExampleClass
{
public virtual Faculty Faculty { get; set; }
}
using System;
using System.ComponentModel;
using System.Data.Entity;
using System.Data.Entity.Migrations;
using System.Linq;
public static class Extensions
{
public static string GetEnumDescription<TEnum>(this TEnum item)
=> item.GetType()
.GetField(item.ToString())
.GetCustomAttributes(typeof(DescriptionAttribute), false)
.Cast<DescriptionAttribute>()
.FirstOrDefault()?.Description ?? string.Empty;
public static void SeedEnumValues<T, TEnum>(this IDbSet<T> dbSet, Func<TEnum, T> converter)
where T : class => Enum.GetValues(typeof(TEnum))
.Cast<object>()
.Select(value => converter((TEnum)value))
.ToList()
.ForEach(instance => dbSet.AddOrUpdate(instance));
}
protected override void Seed(Temp.MyClass context)
{
context.Facultys.SeedEnumValues<Faculty, FacultyEnum>(@enum => @enum);
context.SaveChanges();
}
public class MyClass : DbContext
{
public DbSet<ExampleClass> Examples { get; set; }
public DbSet<Faculty> Facultys { get; set; }
}
var example = new ExampleClass();
example.Faculty = FacultyEnum.Eng;
if (example.Faculty == FacultyEnum.Math)
{
//code
}
If you don't add virtual in Faculty property, you must use Include method from DbSet to do Eager Load
var exampleFromDb = dbContext.Examples.Include(x => x.Faculty).SingleOrDefault(e => e.Id == 1);
if (example.Faculty == FacultyEnum.Math)
{
//code
}
If Faculty property is virtual, then just use it
var exampleFromDb = dbContext.Examples.Find(1);
if (example.Faculty == FacultyEnum.Math)
{
//code
}